As we age, so do our cells. In fact, we can safely say that cellular aging is aging, as cells make up every organ in our body. However, the rate at which our cells die varies from person to person.
Lifestyle factors - such as alcohol consumption, smoking, exercise, or stress - can greatly influence the progression of cellular aging.
Our cells normally react to stimuli from both inside and outside the body, and they do so using a variety of biological pathways. Genetic regulation is one such pathway.
Among other things, our cells contain telomeres, which are repetitive sections of DNA located at the end of chromosomes. Telomeres protect chromosomes from deteriorating, which has been likened to the way that the tips of shoelaces protect them from fraying.
Telomere length has been associated with aging and disease. As we age, telomeres become shorter and shorter until the cells die or transform into oncogenic cells. Short telomeres have been linked with cancer, heart disease, and diabetes.
Researchers at University of California-San Diego (UCSD) - led by Aladdin Shadyab, Ph.D., from the Department of Family Medicine and Public Health at UCSD School of Medicine - examined the effects of a sedentary lifestyle on cell "age" in elderly women.
The findings were published in the American Journal of Epidemiology.
Assessing the link between telomeres, exercise, and biological age
Researchers evaluated the link between leukocyte telomere length (LTL) and sedentary time in 1,481 older women, who were either white or African-American, from the Women's Health Initiative - a cross-sectional, longitudinal study from 2012-2013, which examined the factors that determine chronic diseases in postmenopausal women.
The women were, on average, 79 years old.
The sedentary time was assessed using both self-reporting and an accelerometer. Participants filled in questionnaires and had their movements tracked by an accelerometer that they wore on their right hip for 7 days in a row.
Shadyab and team examined the association between LTL and sedentary time using multiple linear regression models. They also investigated whether the associations varied by how much moderate- to vigorous-intensity physical activity the participants engaged in daily.
The scientists adjusted the results for variables such as lifestyle and health-related factors, as well as demographics and body mass index (BMI).
Sedentary women biologically older by 8 years
Women who exercised for under 40 minutes and were sedentary for more than 10 hours per day had biologically "older" cells than women who were less sedentary and exercised more.
Specifically, low physical activity seemed to account for an 8-year biological age gap between those who exercised and those who did not.
"Our study found cells age faster with a sedentary lifestyle. Chronological age does not always match biological age," says Shadyab.
According to Shadyab, this is the first time that a study has investigated the link between sedentary time, exercise, and telomeres. He also highlights the importance of lifestyle choices on telomere length and aging.
"We found that women who sat longer did not have shorter telomere length if they exercised for at least 30 minutes a day, the national recommended guideline. Discussions about the benefits of exercise should start when we are young, and physical activity should continue to be part of our daily lives as we get older, even at 80 years old."
Aladdin Shadyab, Ph.D.
The authors also suggest that future studies should examine whether cardiorespiratory fitness changes the relationship between sedentary time and LTL, as well as how exercise affects telomere length in young people.
Associations of accelerometer-measured and self-reported sedentary time with leukocyte telomere length in older women, Aladdin H. Shadyab et al., American Journal of Epidemiology, doi:10.1093/aje/kww196, published online 19 January 2017.
UCSD news release, accessed 18 January 2017 via EurekAlert.
National Institute on Aging, What is aging?, accessed 18 January 2017.
Telomeres, lifestyle, cancer, and aging, Masood A. Shammas, Current Opinion in Clinical Nutrition & Metabolic Care, doi:10.1097/MCO.0b013e32834121b1, published online January 2011.
United States National Library of Medicine, Telomeres, accessed 18 January 2017.